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from the Mr.-Magneto,-come-here,-I-want-to-see-you dept.
Scientists have, for the first time, created a permanently magnetic liquid.
[Senior author Thomas Russell, a distinguished professor of polymer science and engineering at the University of Massachusetts Amherst] and his team created these liquid magnets by accident while experimenting with 3D printing liquids at the Lawrence Berkeley National Laboratory (where Russell is also a visiting faculty scientist). The goal was to create materials that are solid but have characteristics of liquids for various energy applications.
Russell leads the program "Adaptive Interfacial Assemblies Towards Structuring Liquids", which focuses on developing a new class of materials – 3D-printable all-liquid structures - at Berkeley Lab’s Materials Sciences Division.
Post Doctoral student and Lead Author Xubo Liu noticed unexpected behavior in one 3D-printed material made from magnetized particles spinning in unison on a magnetic stir place. After additional investigation
Using a technique to 3D-print liquids, the scientists created millimeter-size droplets from water, oil and [20 nanometer diameter iron-oxide particles]. The liquid droplets keep their shape because some of the iron-oxide particles bind with surfactants — substances that reduce the surface tension of a liquid. The surfactants create a film around the liquid water, with some iron-oxide particles creating part of the filmy barrier, and the rest of the particles enclosed inside, Russell said.
The team then placed the millimeter-size droplets near a magnetic coil to magnetize them. But when they took the magnetic coil away, the droplets demonstrated an unseen behavior in liquids — they remained magnetized. (Magnetic liquids called ferrofluids do exist, but these liquids are only magnetized when in the presence of a magnetic field.)
The scientists have not determined exactly how the liquid is retaining the field, but once this is fully understood a variety of applications present according to Russell, for example:
printing a cylinder with a non-magnetic middle and two magnetic caps. "The two ends would come together like a horseshoe magnet," and be used as a mini "grabber," he said.
In an even more bizarre application, imagine a mini liquid person — a smaller-scale version of the liquid T-1000 from the second "Terminator" movie — Russell said. Now imagine that parts of this mini liquid man are magnetized and parts aren't. An external magnetic field could then force the little person to move its limbs like a marionette.
Also mentioned are potential applications in flexible electronics and drug delivery.
Journal Reference
Science 19 Jul 2019: Vol. 365, Issue 6450, pp. 264-267 DOI: 10.1126/science.aaw8719
(Score: 0) by Anonymous Coward on Thursday July 25 2019, @08:19PM
I'd expect that it stays magnetized for the same reason that solid magnets do; the Brownian Motion or other forces trying to de-align the molecules is weaker than the magnetic field forces trying to keep them aligned. As an example, "why does attaching two magnets allow you to suspect one in mid air just by holding the other one." Admittedly this is more difficult for a liquid than a solid due to how much easier it is for those molecules to move, but the fact they are millimeter-sized drops probably helps with this.
It's some interesting basic science, though. I wonder if any interesting new discoveries or practical uses may come from this.